1. Field of the Invention
The present invention relates to colored fine resin particles and a production process thereof, an aqueous dispersion of the colored fine resin particles and a production process thereof, an ink, an ink cartridge, a recording unit, an ink-jet recording apparatus, and an ink-jet recording process. More particularly, the colored fine resin particles and the aqueous dispersion thereof are useful as, for example, coloring materials for ink-jet inks.
2. Related Art
As coloring materials in the conventional inks used in ink-jet recording method, for example, water-soluble dyes are used. However, recorded images by such an ink are required to more improve water fastness. Many of the water-soluble dyes to date are insufficient in weather fastness, and so it is also simultaneously required to more improve the weather fastness. In reply to these requirements, as means for improving the water fastness and weather fastness of recorded articles, there is a technique in which a pigment is used as a coloring material, and the pigment is dispersed in water to provide an ink. However, it is difficult to reconcile the dispersion stability of a pigment with the ejection stability of ink-jet recording. In addition, there is room to still improve the rub-off resistance of recorded images obtained by pigment inks on, particularly, plain paper.
Many means for improving these problems have been proposed to date. For example, there is a technique in which a resin is added to a pigment ink for the purpose of improving the rub-off resistance. However, a problem that the viscosity of the ink is increased by the resin added has been left. Although a technique in which resin particles are added for the purpose of reducing the viscosity increase of the ink has been proposed, the improvement in rub-off resistance has been insufficient because the ink is in a state that the resin particles and the pigment are separately dispersed therein.
On the other hand, a technique in which a pigment is coated with a resin has been proposed. A technique in which the adsorptivity of such a resin to the pigment is improved by controlling the hydrophobic moiety and hydrophilic moiety of the resin has come to be proposed. However, a portion of the resin, which is not adsorbed on the pigment, but suspends, remains in the ink system according to a production process of mixing the pigment and the resin with each other, whereby in some cases, viscosity increase of the resulting ink has been brought on, or the ejection stability of the ink has been impaired. As a production process by which such a free resin is not caused to remain, a technique in which a pigment is added at a stage of a monomer prior to the preparation of a resin, and the monomer is polymerized in the presence of the pigment to coat the pigment with the resin has been proposed.
For example, Japanese Patent Application Laid-Open No. 9-279073 discloses a technique in which a coloring material having affinity for an unsaturated monomer is added to this monomer, and the resultant mixture was subjected to emulsion polymerization to obtain colored fine resin particles, while Japanese Patent Application Laid-Open No. 11-12512 discloses a technique in which a pigment is added to an ethylenically unsaturated monomer, and the resultant mixture was subjected to emulsion polymerization to obtain an ink for ink-jet.